1.Field of the Invention
The present invention relates to an automatic processing machine in which an exposed photosensitive material is subjected to development processing by being sequentially immersed in a developing solution, a fixing solution, and washing water while being nipped and conveyed by a plurality of conveying rollers, and thereafter, the processed photosensitive material is dried in a drying section, and also relates to a method for manufacturing the conveying rollers used in the automatic processing machine.
2.Description of the Related Art
In an automatic processing machine, an exposed photographic photosensitive material (hereinafter referred to simply as a photosensitive material) is subjected to development processing by being conveyed in such a manner as to be sequentially immersed in a developing solution, a fixing solution, and washing water. The photosensitive material having been conveyed through the washing water is dried in a drying section and is discharged from the automatic processing machine.
Here, squeeze rollers are disposed in a crossover portion between adjacent processing tanks in which processing solutions are respectively filled, so as to decrease the amount of processing solutions applied to the photosensitive material in an upstream processing tank and further transferred to a downstream processing tank. Further, squeeze rollers are disposed at the downstream side of a washing tank and are adapted to squeeze out water on the photosensitive material before the photosensitive material is transferred to the drying section.
It is observed that dotted or streaked marks are sometimes formed on the photosensitive material discharged from the automatic processing machine. When such marks are formed on an X-ray film, particularly, there is a possibility that a diagnosis which demands high precision can be interfered. As a result of examining the cause by which such marks or stains occur, it was confirmed that squeeze rollers have a role in causing such marks.
In such conventional squeeze rollers, as is well known, a soft silicon roller having a high water repellency and a hard phenol roller opposed thereto are used.
The water squeezed out by the squeeze rollers may remain between these rollers.
Since the photosensitive material passes through a fixing solution in the development process, fixing components contained in the fixing solution (that is, thiosulfate and the like) are inevitably mixed in the remaining water. The fixing components are dried and concentrated by drying air leaked from the drying section disposed on the downstream side of the squeeze rollers, and remain as spots on the squeeze rollers. As a result, when water is squeezed out from the next conveyed photosensitive material, spot marks are transferred to the material which affect adversely the finished state of an image subjected to development processing.
As measures against the aforementioned, there is a method in which the squeeze rollers are caused to run idle at a predetermined timing to disperse water over the entire surface of the rollers so that water containing fixing components does not remain between the squeeze rollers. However, this method cannot completely prevent the occurrence of the spot marks.
The above-described phenomenon is noticeably seen when relatively new rollers are used, that is, when an almost new automatic processing machine is used, or when rollers are replaced with new ones.
Generally, a silicon roller used as one of the squeeze rollers in an automatic processing machine has a high water repellency, and even if such squeeze rollers are caused to run idle, the surface tension of a water drop keeps the water drop as it is without being dispersed over the entire surface of the one roller, thereby causing formation of spot marks. Accordingly, occurrence of spot marks may be prevented by making the contact angle of a water drop on the roller of the squeeze rollers smaller.
In order for the water to be dispersed on the roller, it suffices that a roller having a high water absorbing ability be employed. However, a roller having a water absorbing surface tends to be contaminated with the passage of time, and therefore, maintenance becomes complicated.
Further, the present inventors have further examined the cause of formation of spot marks, and as a result, they have found that spot marks are formed probably because low molecular weight silicon present in a silicone rubber polymer which is a main component of a silicone rubber roller used as one of the squeeze rollers, volatilizes toward the peripheral surface of the roller and is transferred to the photosensitive material in contact with the squeeze rollers, to thereby cause a the sensitization on the photosensitive material in which the transferred silicon serves as a core thereof.